1. Field of the Invention
The present invention relates generally to semiconductor integrated circuits. More particularly, the invention relates to semiconductor integrated circuits including a fuse and/or an anti-fuse.
2. Description of the Related Art
A semiconductor integrated circuit such as a memory device and a logic device may utilize a trimming circuit or a redundancy circuit to remedy the effects of certain circuit defects commonly generated during fabrication. For example, a redundant circuit is sometimes fabricated in parallel with a primary circuit. The primary circuit is then tested, and if it is functioning properly, the redundant circuit may be removed or isolated from the overall device. In contrast, if the primary circuit is defective, the redundant circuit, or a portion of the redundant circuit may be enabled to operate in place of or in conjunction with the primary circuit.
Programmable fuses and/or anti-fuses are conventionally used to alternately enable or isolate a redundant circuit. In this context, a fuse is a low resistance element that may be permanently programmed into a high resistance state, whereas an anti-fuse is a high resistance element that may be permanently programmed into a low resistance state. For example, if a primary circuit is found to be operating normally (i.e., is non-defective), a corresponding redundant circuit may be isolated from the primary circuit by applying energy to one or more programmable fuse(s), thereby forming an open circuit between the primary circuit and redundant circuit. On the other hand, if the primary circuit is found to be defective, the redundant circuit may be operationally included with (or substituted for) the primary circuit by applying energy to programmable anti-fuse to form a closed circuit electrically bridging the primary circuit with the redundant circuit. In addition to selective enablement of redundant circuits, fuses and anti-fuses may alternately or additionally be used in conjunction with program trimming circuits, such as resistive trimming circuits.
Laser energy or electrical energy is typically used to program fuses and anti-fuses. The use of laser energy is generally limited to sequential programming processes for fuses and anti-fuses, but such processes take considerable time. In addition, laser systems are quite expensive and their operation sometimes results in contamination problems. Programming with electrical energy, on the other hand, is relatively quick, inexpensive, and creates no contamination issues. As such, electrical programming has been predominantly used in the fabrication of semiconductor devices.
For the electrical programming, it is desirable that the ratio of fuse and anti-fuse resistance after programming be higher than before programming. It is also desirable for the applied electrical power to be relatively low power and its application to be relatively short in duration.
An electrical fuse may be implemented using with a transistor, (i.e., a transistor type electrical fuse). By selectively breaking down the gate insulation layer of a transistor type electrical fuse, an anti-fuse type transistor can be provided. When a transistor is used as the electrical fuse, although the constituent gate insulation layer of the transistor may have a thickness of about 24 Å this very thin gate insulation layer may nonetheless have a high dielectric breakdown voltage of 4.5 to 4.8V.
Since the high dielectric breakdown voltage associated with a transistor type electrical fuse requires a correspondingly high voltage and current driving capability of a control circuit, the control circuit will occupy a relatively large area of an incorporating semiconductor device. Thus, it may be difficult to improve the integration density of an integrated circuit device incorporating the control circuit. In addition, application of the high dielectric breakdown voltage may cause related programming failures. Furthermore, the reliability of a corresponding driving circuit may deteriorate under the effects of a relatively high voltage required for fuse programming.